Hansen insists he just wants the truth of his mother's disappearance to finally be heard and his father's culpability to be legally settled. He acknowledges, however, there are several million dollars at stake.

"I want justice for my mother. I want her story to be told," Hansen told ABCNews.com. "I don't want this to be swept under the rug like it has been for the last 47 years."

Hansen says he was raised by his father telling him and his two siblings that his mother had deserted the family, but a very different story emerged when he began researching his mother's story 15 years ago.

What Hansen found was divorce papers that indicated violence between his parents, and the fact that his mother was reported missing when she didn't show up for a hearing regarding the separation. In addition, his mother's friends who knew her at the time of her disappearance said she had vowed she'd never desert her kids.

Patricia Martin, one of Joan Hansen's best friends, claims she spoke to Joan Hansen moments before she was murdered.

"We were speaking on the phone and all of sudden Joan said 'Oh my God,' then there was silence and then I heard her holler 'Don't!'" said Martin, 76. "She kept saying 'he's coming' and then she started screaming and the phone went dead."

"I have no doubt what happened to Joan," said Martin. "I know he killed her."

Son Confronts Dad, Calls Him 'A Killer'

Hansen said that no matter whom he talked to – his father's friends, his mother's lawyer and even aunts he never knew existed – everyone told him the same story.

"They all say, well your dad killed your mom and he probably buried her down there at the barn site," said Hansen, who is now 50 and living in Costa Mesa, Calif., where he works as a self-employed house painter.

King County Sheriff's office spokesman Sgt. John Urquhart told ABCNews.com that Robert Hansen has always been and will continue to be a "person of interest" in his wife's case, even now that he's deceased.

"She's gone, she's disappeared, and we believe she's been a victim of a homicide," said Urquhart. "We've been investigating him for years and years, a long, long time."

Urquhart said Robert Hansen was never arrested because there was never enough "probable cause" to do so.

Hansen believes that his mother was buried in the days following her Aug. 8, 1962 disappearance underneath a cement slab in the family barn, but that the area has since been paved over by a major state highway.

Despite employing cadaver dogs, ground-penetrating radars and even convincing the King's County Sheriff's office to excavate a portion of the road, his mother's body has never been discovered.

While Hansen continued on his search for the truth about his mother, he says his father became increasingly estranged from him, eventually wanting "nothing to do" with his son. It culminated with the father writing Ty Hansen out of his will and leaving his estate to a "friend in Costa Rica," according to ABC's Seattle affiliate KOMO.